This invention relates in general to machines utilized in packaging operations, and more particularly a machine for maintaining flexible sidewalls of a container in a predetermined configuration, so that some other operation may be performed on the container.
Many food and other products are packaged in composite containers composed of paperboard side walls and metal or plastic end walls. Usually these containers are assembled by the container manufacturer, at least to the extent that the contents may be introduced into them. For example, the container manufacturer may ship the container to the packager with a bottom wall attached to the paperboard side walls, but with top wall detached. After filling the container, the packager attaches the top wall. Sometimes, the top wall has a large opening fitted with a removable cap, as is the case of powdered cocoa and tea containers, and in that situation the container manufacturer assembles the entire container, except for the cap which is applied by the packager.
In any event, the present procedure necessitates shipping erected containers which, although light in weight, consume considerable space. Consequently transportation expenses are high.
To reduce transportation expenses, procedures and special machines now exist for enabling the packager to erect the containers. The container manufacturer in this instance supplies paperboard blanks, which are shipped to the packager flat. The container manufacturer also provides a machine for transforming the flat blanks into open top containers. The machine folds each blank and glues its margins to provide a container of rectangular configuration, with the four side walls and the bottom wall being intergral. Thereafter, a plastic fitment ring is attached to the upper margin of the container, and this ring has a large opening capable of receiving a plastic cap. No machine has yet been developed for efficiently applying the fitment ring to the upper margin of the container.
The difficulty in applying the fitment ring is attributable primarily to the flexibility of the paperboard. In this regard the fitment ring has a downwardly opening groove into which the upper edge of the paperboard container fits. Once the fitment ring is in place, both ends of the container are quite rigid, notwithstanding the flexibility of the paperboard itself, for the lower end is rigidified by the integral bottom wall, while the upper end is rigidified by the fitment ring. The problem resides in bringing the flexible upper margin of the container into a configuration which corresponds precisely to that of the groove in the fitment ring and maintaining the upper margin in that configuration as the fitment ring is applied.